1. Field of the Invention
The present invention relates to a method of producing nonionic surfactants low in alkylene oxide content and low in 1,4-dioxane, by a catalytic method employing an alkali metal fatty alkoxide. It also relates to a method of production of alkali metal fatty alkoxide.
2. Discussion of the Background
Because products containing nonionic surfactants are used essentially daily, and in view of the possible toxicological hazard of appreciable impurities of alkylene oxides and 1,4-dioxane in these surfactants, it is necessary to have a supply of products having very low levels of alkylene oxides and 1,4-dioxane.
The customary production of nonionic surfactants employs catalysis with Na ions and/or K ions added to such reactants as alkylphenols, fatty alcohols, glycols, amines, fatty acids, and oils. Preferably the Na and/or K ions are added to the form of NaOH, KOH, sodium methoxide, or potassium methoxide. After establishing an inert atmosphere over the reaction medium water of solution and water of reaction are removed from the reaction medium with nitrogen. Then the reaction with added alkylene oxide is carried out.
According to U.S. Pat. No. 4,453,023 barium alkoxides can also be used as catalysts. These alkoxides are produced, according to said U.S. Patent, by reaction of barium metal with ethanol, followed by reaction with, e.g., ethylhexanol. Vacuum distillation is used to remove ethanol from the barium ethylhexanoxide which is produced.
Eur. Pat. 0 026 547 describes a similar catalyst preparation technique in which alkoxides of Ca, Sr, or Ba are prepared by reacting Ca, Sr, or Ba metal with ethanol, followed by reaction with decanol. The regenerated ethanol is then removed by applying a vacuum.
There are disadvantages associated with the method of producing nonionic surfactants according to the method described in U.S. Pat. No. 4,453,023 in which the catalyst employed is prepared by the two-step method wherein an alkali metal is reacted with ethanol, followed by reaction of the metal ethoxide with a higher alcohol. The disadvantages are very high costs, as well as a high residual content of alkylene oxides (c. 30 ppm) and 1,4-dioxane (c. 120 ppm). Further, there are problems associated with the use of metals for producing alkoxides, because of the liberation of water; and products produced with ethylhexanoxide catalysts have a strong odor of ethylhexanol. A need therefore continues to exist for a method of preparing nonionic ethoxylated surfactants low in alkylene oxides and low in 1,4-dioxane.